This invention relates to the preparation of zirconium- and platinum-containing materials, particularly films on substrates such as semiconductor device structures.
Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. This is at least because many of the Group VIII metal films are generally unreactive, resistant to diffusion of oxygen and silicon, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent.
Thus, films of Group VIII metals and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as the plate (i.e., electrode) itself in capacitors. In addition, Group VIII metals are useful in catalysts.
Platinum is one of the candidates for use as an electrode for high dielectric capacitors. Capacitors are the basic charge storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs). It is important for device integrity that oxygen and/or silicon not diffuse into or out of the dielectric material. This is particularly true for ferroelectric RAMs because the stoichiometry and purity of the ferroelectric material greatly affect charge storage and fatigue properties. Also, oxidation of the underlying silicon will result in decreased series capacitance, thus degrading the cell capacitor.
In order to function well in a bottom electrode, the electrode film or film stack must be able to withstand the high temperature anneals required to recrystallize the dielectric layer. As stated above, platinum is one of the candidates for use as an electrode material for high dielectric capacitors. Platinum, alone, however, in the form of films deposited by chemical vapor deposition techniques can be unstable when annealed at temperatures 650xc2x0 C. and above. For example, as shown in FIG. 1, a platinum layer can form islands during the anneal process, which suggests high mobility of platinum at temperatures far below its melting temperature. One solution is to combine (e.g., alloy) the platinum with rhodium to enhance the barrier properties and stability of the layer; however, rhodium precursors can be very expensive.
Thus, there is a continuing need for methods and materials for the deposition of stable platinum-containing films, particularly those that can be subjected to relatively high annealing temperatures.
The present invention is directed to methods for forming materials containing both zirconium and platinum. Preferably the materials are films deposited on substrates, such as those formed in the manufacture of a semiconductor device, such as a ferroelectric device. The substrates are preferably semiconductor substrates or substrate assemblies. Preferably, the films are formed by various vapor deposition techniques, preferably, chemical vapor deposition techniques.
Significantly and preferably, the zirconium, which is typically in the form of an oxide (zirconia) stabilizes the platinum film, such that upon annealing at temperatures of at least about 650xc2x0 C. there are substantially no signs of island formation. Thus, zirconium serves to mechanically stabilize platinum films against migration during annealing. Surprisingly, this occurs without substantially degrading the conductivity of the film.
Typically and preferably, the films are electrically conductive. The resultant film can be used as an electrode in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device. The platinum-zirconium films (i.e., layers) overcome some of the problems associated with the use of platinum alone as an electrode material, without adversely affecting the properties of the platinum layer, such as its electrical conductivity.
Other materials that can be formed using the present invention include catalyst materials. Such materials typically include a roughened surface (e.g., a surface that includes a plurality of columnar pedestals, preferably that are at least about 400 Angstroms tall).
In the context of the present invention, the term xe2x80x9cmetal-containing filmxe2x80x9d includes, complexes of zirconium and platinum with other elements (e.g., O, N, and S), particularly oxygen, and/or other metals or metalloids. Zirconia (ZrO2) is a particularly desirable component of a metal-containing film because of its ability to stabilize platinum films against migration during annealing without substantially degrading the conductivity of the film, as described herein.
One preferred method of the present invention involves forming a film on a substrate, such as a semiconductor substrate or substrate assembly during the manufacture of a semiconductor structure. The method includes: providing a substrate (preferably, a semiconductor substrate or substrate assembly); providing a precursor composition that includes one or more zirconium complexes; providing a precursor composition that includes one or more platinum complexes; and forming a platinum-zirconium-containing film from the precursor compositions on a surface of the substrate (preferably, the semiconductor substrate or substrate assembly). Preferably, the precursor composition that includes one or more zirconium complexes is the same as the precursor composition that includes one or more platinum complexes.
In certain embodiments, the process is carried out in a nonhydrogen atmosphere (i.e., an atmosphere that does not include H2), and preferably in an oxidizing atmosphere. Using such methods, the precursor complexes of zirconium and platinum are converted in some manner (e.g., decomposed thermally while ligands are oxidized) and deposited on a surface to form a metal-containing film. Thus, the film is not simply a film of the complex of the precursors. Herein, xe2x80x9cplatinum-zirconium filmxe2x80x9d and xe2x80x9cplatinum-zirconium-containing filmxe2x80x9d are used interchangeably. Preferably, such films are in the form of a platinum-zirconia-containing film, also referred to herein as a platinum-zirconia (Ptxe2x80x94ZrO2) film.
Preferably, the precursor complexes are neutral complexes and may be liquids or solids at room temperature. Typically, however, they are liquids. If they are solids, they are preferably sufficiently soluble in an organic solvent or have melting points below their decomposition temperatures such that they can be used in flash vaporization, bubbling, microdroplet formation techniques, etc. However, they may also be sufficiently volatile that they can be vaporized or sublimed from the solid state using known vapor deposition techniques including chemical vapor deposition and atomic layer deposition techniques. Thus, the precursor compositions of the present invention can be in solid or liquid form. As used herein, xe2x80x9cliquidxe2x80x9d refers to a solution or a neat liquid (a liquid at room temperature or a solid at room temperature that melts at an elevated temperature). As used herein, a xe2x80x9csolutionxe2x80x9d does not require complete solubility of the solid; rather, the solution may have some undissolved material, preferably, however, there is a sufficient amount of the material that can be carried by the organic solvent into the vapor phase for chemical vapor deposition processing.
The methods described herein preferably involve the use of vapor deposition techniques such as chemical vapor deposition and atomic layer deposition, although this is not a requirement for all embodiments. That is, for certain embodiments, sputtering, spin-on coating, etc., can be used.
The present invention also provides a capacitor. In one embodiment, the capacitor includes: a first conductive layer; a dielectric material on at least a portion of the first conductive layer; and a second conductive layer on the dielectric material; wherein at least one of the first and second layers includes a platinum-zirconium film (preferably, a vapor-deposited film, i.e., a film deposited by vapor deposition methods that includes platinum and zirconium, preferably in the form of platinum-zirconia (Ptxe2x80x94ZrO2)).
The present invention also provides an integrated circuit that includes a capacitor. In one embodiment, the capacitor includes: a first conductive layer; a dielectric material on at least a portion of the first conductive layer; and a second conductive layer on the dielectric material; wherein at least one of the first and second conductive layers includes a (preferably, vapor-deposited) platinum-zirconium film.
The present invention also provides a memory cell. In one embodiment, the memory cell includes: a transistor; and a capacitor that includes a (preferably, vapor-deposited) platinum-zirconium film. Preferably, the capacitors are as described above.
The present invention also provides methods of fabricating capacitors. In one embodiment, a method involves: forming a first conductive layer; forming a dielectric layer on at least a portion of the first conductive layer; and forming a second conductive layer on the dielectric layer; wherein at least one of the first and second conductive layers includes a (preferably, vapor-deposited) platinum-zirconium film. Preferably, the conductive layer is formed by chemical vapor codeposition of platinum and zirconium precursor compositions.
In another embodiment of a method for fabricating a capacitor having a first and a second electrode, the method includes: providing a substrate; forming an insulative layer overlying a substrate; forming an opening in the insulative layer to expose the substrate; forming a conductive plug in the opening, the conductive plug forming a first portion of the first electrode of the capacitor, the conductive plug recessed below a surface of the insulative layer; forming a first conductive layer in the opening and overlying the conductive plug such that the first conductive layer is surrounded on sidewalls by the insulative layer, the first conductive layer forming a second portion of the first electrode, the first conductive layer being formed of a (preferably, vapor-deposited) platinum-zirconium film; and forming a second conductive layer overlying the first conductive layer, the second conductive layer forming a third portion of the first electrode. Preferably, the method further includes: creating a dielectric layer on the second conductive layer, the first conductive layer substantially preventing oxidation of the dielectric layer; and creating the second electrode overlying the dielectric layer, the first and the second electrode and the dielectric layer forming the capacitor. Preferably, forming the second electrode includes sputtering an electrically conductive material to overly the dielectric layer. Preferably, forming the first conductive layer includes: admitting a platinum precursor composition to a chemical vapor deposition reaction chamber; admitting a zirconium precursor composition to the chemical vapor deposition reaction chamber; and applying sufficient reaction gas to the chemical vapor deposition reaction chamber to cause co-deposition of platinum and zirconium. Preferably, the method further includes planarizing the insulative layer prior to forming the conductive plug. Preferably, forming the conductive plug includes depositing in-situ doped polysilicon in the opening.
In another embodiment, there is a method of manufacturing a catalyst, the method includes: providing a substrate; providing a precursor composition including one or more zirconium complexes; providing a precursor composition including one or more platinum complexes; and forming a platinum-zirconium-containing material from the precursor compositions on a surface of the substrate to form a catalyst. Preferably, forming a platinum-zirconium-containing material occurs in the presence of an oxidizing gas.
The present invention also provides a method of stabilizing a platinum film upon annealing the film at temperatures at least about 650xc2x0 C., the method includes incorporating zirconium into the platinum film. Preferably, the zirconium is at least partially oxidized. As used herein, xe2x80x9cstablexe2x80x9d means that there are substantially no signs of island formation after annealing the platinum-zirconium film at a temperature of at least about 650xc2x0 C. Significantly and advantageously, this zirconium incorporation preferably does not substantially degrade the conductivity of the platinum film.
Preferably, in the methods and articles described herein, the platinum-zirconium films are platinum-zirconia films (Ptxe2x80x94ZrO2-containing films). Typically, whether partially or completely oxidized or including other elements, the films include platinum and zirconium in a ratio of platinum(x):zirconium(1xe2x88x92x), wherein x is in the range of about 0.99 to about 0.01. Preferably, the dielectric layer is selected from the group consisting of tantalum pentoxide (Ta2O5), Barium Strontium Titanate (BST), Strontium Titanate (ST), Lead Zirconium Titanate (PZT), Strontium Bismuth Tantalate (SBT) and Bismuth Zirconium Titanate (BZT).
In the methods described herein, preferably, the platinum precursor composition includes a platinum complex selected from the group consisting of CpPt(Me)3, wherein Me is a methyl group and Cp is substituted or unsubstituted cyclopentadienyl, Pt(CO)2Cl2, cis-Pt(CH3)2[(CH3)NC]2, (COD)Pt(CH3)2, (COD)Pt(CH3)Cl, (C5H5)Pt(CH3)(CO), (acac)(Pt)(CH3)3, Pt(acac)2, Pt(PF3)4, wherein COD=1,5-cycloctadiene and acac=acetylacetonate (CH3C(O)CHxe2x95x90C(O)CH3), and mixtures thereof. More preferably, the platinum precursor composition includes CpPt(Me)3, wherein Me is a methyl group and Cp is methyl cyclopentadienyl (also written as MeCp). Preferably, the platinum complexes do not include halogen atoms.
In the methods described herein, preferably the zirconium precursor composition includes one or more complexes of zirconium tert-butoxide (Zr(OC(CH3)3)4), zirconium butoxide (Zr(O(CH2)3CH3)4), zirconium propoxide Zr(O(CH2)2CH3)4), and zirconium acetylacetonate (Zr(acac)4), and mixtures thereof.
Methods of the present invention are particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. It is to be understood that methods of the present invention are not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) and silicon on glass can be used as well. Also, the methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in methods of the present invention. These include, for example, fibers, wires, etc., as well as substrates used in catalytic systems, such as catalytic converters in automobiles. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon.